1. Field of the Invention
The present invention relates to a license plate image-pickup device and an image exposure adjustment method, and more particularly to the license plate image-pickup device and the image exposure adjustment method that adjust the exposure of the license plate image.
2. Description of Related Art
As scientific investigation becomes popular, intersection surveillance monitors are used to clarify the attribution of responsibility in many car accidents occurred in big cities. However, the density of installing the monitors is limited, and images of the accident scene cannot be recorded clearly in some situations. In addition, once a car enters into suburbs or scenic areas, the installation of monitors is rare. Once a car accident occurs, a policeman or investigator is required to go to the scene to clarify the attribution of responsibility. Therefore, the installation of a driving recorder in a car becomes increasingly popular, so that our legal rights can be protected in critical moments. In general, the driving recorder has the image recording and storage functions, and some driving recorders even come with a sound recording function.
When a car accident occurs, the image of the driving recorder can reproduce the actual situation of the car accident to assist the police or related unit to know the actual situation, and the license plate data contained in the image can be used as a line to hunt for the car accident perpetrator. To clearly show the license plate data, some driving recorders use an automatic exposure adjustment to achieve the purpose. However, some of the conventional automatic exposure adjustment modules of the driving recorders use the brightness of the whole image as a reference base or use a high dynamic range imaging (HDRI) method to adjust the exposure of the image. The effect is very limited, since the environment is changed so quickly.
In view of the aforementioned problems, it is an urgent issue for related designers and manufacturers to design and produce a license plate image-pickup device and an image exposure adjustment method thereof to show the license plate image clearly. With the pixel-based complementary metal oxide semiconductor sensor (pixel-based CMOS sensor) technology, the inventor of the present invention designs a license plate image-pickup device and an image exposure adjustment method thereof in accordance with the present invention to overcome the drawbacks of the prior art.